1. Field of the Invention
This invention relates to an apparatus for controlling filament wrapping of a spun core yarn.
2. Description of the Prior Art
In the prior art there has been increasing interest for the production of filament wrapped core-spun yarns and methods development related to said yarn production. Grosicki and Chylewska, Textile Institute and Industry Journal 17, pages 288-289, August 1979 are among the more recent researchers reporting their work in the field of core-spun yarns. These researchers utilize an air-vortex system to produce a core-spun yarn whereby the core is continuous filament yarns with a sheathing of natural fibers. While the benefits of their type yarn are cited the apparatus requires major mill modifications and uses vacuum in production which are undesirable for spinning mills equipped with ring spinning frames. Audivert and Fortuny, in the same issue as the cited work of Grosicki and Chelewska, discuss production of another means to produce a core-wrap type yarn called Differential Twist Yarns. The advantages of producing such yarn were enhanced tenacity and high production rate but the method requires a false-twist tube and is highly dependent on twist imparted to the yarn. Differential Twist Yarns are produced by first combining filament and staple fibers in the drafting zone then twisting further in the balloon zone with another filament. Three components are essential to the method of yarn production.
Audivert, U.S. Pat. No. 3,722,202, describes a method for producing blended yarns containing a staple fibrous core and a continuous man-made filament that is achieved on a ring spinning frame. In the Audivert process, feeding tension on the filament is important to the extent that not more than 0.5 g/tex should be employed. In the Audivert method, apparatus employed to obtain or control tension is not described nor are means to adjust tension described to achieve desired effect in the resultant composite wrapped yarn. Audivert, nevertheless claims a feeding tension is required in his method to produce desired effect of blending to obtain a wrapped yarn. To obtain tension on the filament, obviously a drag force must be used. Tensioning devices are inherent and require constant monitoring to assure binding effects are obtained with no part of the filament sinking into the fibrous core. Furthermore, Audivert teaches erroneous feeding methods which result in filament processed into the internal structure of the core yarn.
In contradistinction to prior devices, Parker, U.S. Pat. No. 2,552,210, avoided tensioning devices by merely feeding filament tension free. Parker accomplished tension free feeding through use of an upside down cone containing the filament yarn and points out tension is inevitable where a spun or twisted thread must turn a bobbin or spool for delivery. By employing the teachings of Parker, utilizing a tension free process, the filament goes into and out of the core as it is being spun thus partially covering the filament yarn.
An additional problem in the practice of the prior art is the point of combination of the filament with the core yarn. It is critical for the combination to occur at a sufficient distance from the exit of the nip of the front rolls of the drafting system of a ring spinning frame to preclude the filament from going into and out of the core as it is being spun, which is the object of Parker's teachings. The prior art teaches that the filament is combined with the staple fibers just as the two emerge from the front rolls of the spinning frame. Alternatively, the filament is passed through the apron rolls then through the front rolls. When passage through apron rolls occurs, the rolls must have a recessed center for slip drafting. None of the prior art can be practiced without considerable control and monitoring of tension. Further, no teachings of the prior art address the inherent problem of intertwining of the filament while the core is being spun because of the location of the combination point of the filament and the core yarn at the nip of the front rolls.